Is Milk Kosher?

It seems there is renewed discussion over whether milk (both Chalav Yisrael and plain milk) is kosher. The reason is that the percentage of non-kosher cows, particularly milking cows, discovered after slaughter is somewhere above 30% (some estimates are as high as 90%). If that is the case, then a large portion of milk comes from non-kosher cows and is therefore not kosher. The way milk is processed is that milk from a number of cows is mixed together. If milk in general is at least 30% non-kosher, then any mixture of milk -- which is what reaches the consumer -- contains at least 30% of non-kosher. The Shulchan Arukh (Yoreh De'ah 81:2) rules that if milk from a non-kosher cow is mixed in with milk from regular cows, the maximum allowed for bitul is one-sixtieth, 1.67%. Evidently, our milk supply contains huge amounts of milk from non-kosher cows, well above the bitul threshold. If this is the case, why is this milk kosher? Or isn't it?

This question was posed in the journal Ha-B'er (Nissan 5763/2003) and responses were published from three prominent scholars in Israel. What follows below are very brief summaries of extensive analyses of the complex concepts of rov and chazakah that, frankly, make my head spin. I apologize if this is not entirely correct. The articles can be found in this file (PDF). I am also including a summary of a recent responsum by R. Yisroel Belsky, which is an internal OU document for which I obtained permission to quote but not to disseminate.

I. R. Zalman Nechemiah Goldberg

R. Zalman Nechemiah Goldberg answered that milk is kosher because we look at each individual cow and, despite the percentage of non-kosher cows, each individual cow is considered kosher until proven otherwise. For example, if there was only one cow left in the world, we would assume that it is kosher and not automatically render it non-kosher based on the above percentage. Therefore, if all the cows in the world were gathered together we would also not assume that there are non-kosher cows among them. The milk is similar to a gathering of all the cows in the world, and we similarly do not assume that there is non-kosher milk in the mixture.

II. R. Asher Weiss

R. Asher Weiss writes that the rules of rov are not the same as statistical probabilities. For example, if one lives in a city that is 60% Jewish and ten men from the city gather to pray, must we say that only 60% of them are Jewish and they lack a minyan? Therefore, since each individual cow is considered kosher, the statistical incidence of non-kosher cows is irrelevant.

III. R. Levi Yitzchak Halpern

R. Levi Yitzchak Halpern points out that most of the cows we render non-kosher are not necessarily technically non-kosher, and are often due to various stringencies and doubts. It is therefore impossible to say what percentage is unquestionably non-kosher and what percentage is possibly non-kosher. Therefore, we have no conclusive proof that contradicts the general rule that most slaughtered animals are kosher.

As noted above, the Shulchan Arukh (Yoreh De'ah 81:2) rules that if milk from a known non-kosher cow is mixed in with milk from regular, unknown cows, the maximum allowed for bitul is one-sixtieth, 1.67%. It is relevant to note that the halakhah requires checking slaughtered cows for problems in their lungs, because the incidence of such problems is 10% or greater. Incidence of other problems (of the 17 problems) is evidently less than 10%. However, if you add them all together, it seems that somewhere between 20-30% are assumed to be non-kosher. Despite this, the Rama allows milks from a known non-kosher cow that is mixed in with milk from unknown but presumably kosher cows in a ratio of 1.67% or less. Evidently, this is because unless known for certain, other cows are presumed kosher despite the 20-30% assumed rate of non-kosher cows.

IV. R. Yisroel Belsky

In a recent responsum, R. Yisrael Belsky ruled that cows have a chezkas kashrus, a presumption of being kosher. Thus, even if a cow is slaughtered and found to be non-kosher, we assume that the problem that rendered this cow non-kosher is a recent development. Therefore, regarding the milk we do not have a known statistical majority of non-kosher milk. Furthermore, none of the milk-producing cows are definitely non-kosher.

R. Belsky also adds that the statistics for non-kosher cows includes many stringencies and doubts, and does not represent a true percentage of non-kosher cows.


It seems that R. Hershel Schachter remains in doubt about this matter and has not been convinced by R. Belsky's arguments.